One afternoon Rep. Danny Davis (D-Ill.) picked up his dry cleaning in the Longworth House Office Building. But when he took his shirts out at home, he noticed something peculiar.

Between the time he dropped off his clothes and picked them up, his shirts improved in quality — the regular cuffs were now French, and they had been nicely tailored.

“I looked at them and I said, ‘This couldn’t possibly be mine, this is too expensive, this is way out of my class,’ ” said Davis.

The clothes really belonged to Rep. David Davis (R-Tenn.); the two Davises had just fallen victim to an all-too-frequent case of mistaken identity.

“I no longer use the laundry here because of that,” said David Davis.

And there’s even more confusion if you share your surname with five other sitting members of Congress.

“This is the first place I’ve ever been in my life where Davis is the most common last name,” said Rep. Artur Davis (D-Ala.). “Normally around here, you get used to the fact that when someone yells out ‘congressman,’ you don’t automatically turn around. But around here, ‘Congressman Davis’ still doesn’t make you turn around.”

The Davises are not the only lawmakers who have it rough. There are 85 members of Congress who share a surname with at least one other member. The most popular surname in Congress is Davis with seven, followed by Miller and Johnson, each with five.

And then there are the Prices, who are often mistaken for each other on legislative matters.

“While David’s [Rep. David Price (D-N.C.)] a wonderful fellow, our politics are significantly different,” said Rep. Tom Price (R-Ga.). “So he would get put on a bill that was more reflective of my district and I would get put on a bill that was much too far to the left for my district.”

Still, David Price notes one advantage with his name — it’s first on the voting board.

“I’m the first one on the board and that’s all that matters to me,” the North Carolinian joked.

Even Rep. Deborah Pryce (R-Ohio) said members often approach her on the floor complaining that she voted wrong, mistaking her for other Prices.

Members say constituents confuse them most. And this confusion can work against them, as in the case of Reps. David Davis and Lincoln Davis (D), both of whom hail from Tennessee but serve on opposite sides of the aisle.

“There are occasions when I will get a blessing-out from a constituent from Tennessee for a vote that he [David Davis] may have cast, and I’m sure he gets some from votes I may have cast since he’s Republican and I’m a Democrat,” said Lincoln Davis.

But mistaken identity isn’t always bad. A lawmaker can use the other member as a scapegoat for a vote that he cast.

“You can say it was the other Davis from Tennessee,” joked Lincoln Davis.

In one case, both first and last names are the same: the two Reps. Mike Rogers, Republicans from Alabama and Michigan.

Most have figured out who is who by now, said the Michigan Rogers’s spokeswoman, Sylvia Warner. But in the first couple of years in office, there were continuous mishaps of mail being delivered to the wrong congressman, misdirected constituent calls, and reporters mistaking one for the other.

“I think people just figured it out over time because it’s such an oddity,” Warner said.

In one of the most interesting cases of mistaken identity, almost three years ago the advocacy group MoveOn.org initiated a protest at Rogers’s district office in Lansing, Mich. The group objected to Rogers’s campaign contributions from then-House Majority Leader Tom DeLay (R-Texas) and had come with financial records in hand. There was only one problem: They had the wrong Mike Rogers.

Speaker’s Lobby employees are confronted with confusion over names as well. When taking card requests from reporters, staff insists that reporters indicate which Mike Rogers they are looking for. If they fail to do so, the card is not delivered.

And there are plenty of family ties among these same-named members, including three sets of brothers, such as the Diaz-Balart brothers, both Republicans from Florida.

“Sometimes I’ll get mail that’s his or vice versa,” said Rep. Mario Diaz-Balart of his brother, Rep. Lincoln Diaz-Balart. “But it’s not the Post Office’s fault. It’s the actual constituent who will write out my name thinking it’s him.”

The other two sets of brothers are Sen. Ken Salazar and Rep. John Salazar, both Democrats from Colorado, and Sen. Carl Levin and Rep. Sandy Levin, both Democrats from Michigan.

Others with common pedigrees include the father and son team of Sen. Edward Kennedy (D-Mass.) and Rep. Patrick Kennedy (D-R.I.). Reps. Mark Udall (D-Colo.) and Tom Udall (D-N.M.) are cousins. And Reps. Loretta Sanchez and Linda Sanchez, both Democrats from California, are sisters.

Beyond surname similarities, Rep. Danny Davis has occasionally gotten confused for the House majority whip, Rep. James Clyburn (D-S.C.). Davis recalled the time a constituent approached him and mistook him for Clyburn. The constituent asked him for money.

“One guy walked up to me and said, ‘Mr. Clyburn, I want $5,000 from your PAC [political action committee],’” Danny Davis said. “I said, ‘Yeah, I want $5,000 from his [Clyburn’s] PAC too.’”

In the end, Davis had some fun with it:

“Then I went to Jim and said, ‘Jim, I want my money. And Jim said, ‘What are you talking about?’ So I told him about the guy who wanted $5,000 and told him I told the guy it wouldn’t be a problem,” Davis said, laughing.

Danny Davis also had issues with Rep. Tom Davis (R-Va.), former chairman of the Oversight and Government Reform Committee.

An active constituent often confused the African-American Danny Davis for the white Tom Davis.

“He’ll call me up and say, ‘What the hell are you doing voting like that on the floor for?’ He’d say, ‘I saw ya! I’m watchin’ ya!’ and I’d say, ‘What the hell are you talking about?’ and he’d tell me and I’d say, ‘No, no, you’ve got me confused, that was my cousin.’ And he’d call back and apologize, saying, ‘Yeah, I checked, you’re right.’”

 And, for the record, Danny Davis and Tom Davis are not cousins.

Jessica Malmgren contributed to this article.