I was wrong about an equal number of Republicans. The number was set at five, with the understanding that Pelosi would appoint a Republican from her eight choices, giving a total of seven Democrats and six Republicans. Quoting from Wikipedia:

On June 30, 2021, the resolution to form the committee passed by a vote of 222 to 190, with all Democratic members and two Republican members, Adam Kinzinger and Liz Cheney, voting in favor. Sixteen Republican members did not vote.[17] The resolution empowered Pelosi to appoint eight members to the committee, and House Minority Leader Kevin McCarthy could appoint five members "in consultation" with Pelosi.[18] Pelosi indicated that she would name a Republican as one of her eight appointees.[19]

On July 1, Pelosi appointed eight members, seven Democrats and one Republican, Liz Cheney (R-WY); Bennie Thompson (D-MS) would serve as committee chair.[20] On July 19, McCarthy announced the five members he would recommend as the minority on the select committee. He recommended that Jim Banks (R-IN) serve as Ranking Member, and minority members be Jim Jordan (R-OH), Rodney Davis (R-IL), Kelly Armstrong (R-ND), and Troy Nehls (R-TX).[21] Banks, Jordan, and Nehls voted to overturn the Electoral College results in Arizona and Pennsylvania. Banks and Jordan had also signed onto the Supreme Court case Texas v. Pennsylvania to invalidate the ballots of voters in four states.[22]

On July 21, Thompson stated in an interview that he would investigate Trump as part of the inquiry into Capitol attack.[23] Hours later, Pelosi said in a statement that she had informed McCarthy that she would reject the recommendations of Jordan and Banks, citing concerns for the investigation's integrity and relevant actions and statements made by the two members. She approved the recommendations of the other three.[24] McCarthy then pulled all of his picks for the committee and stated that he would not appoint anyone on the committee unless all five of his choices were approved.[25][26]

After McCarthy rescinded his recommendations, Pelosi announced on July 25 that she had appointed Adam Kinzinger (R-IL) to the committee.[27][28] Kinzinger was one of the ten House Republicans who voted for Trump's second impeachment.[29]

https://en.m.wikipedia.org/wiki/United_States_House_Select_Committee_on_the_January_6_Attack