Y Combinator is gearing up for its biggest batch of startups ever — more than 100 companies — so it’s no surprise that it’s beefing up its team.

The accelerator program announced today that former Twitch.tv chief executive and cofounder of SocialCam Michael Seibel is moving up to being full-time from a part-time partner at Y Combinator. Same goes for Jon Levy, Y Combinator’s formerly part-time lawyer.

But it’s also adding a new part-time partner, and arguably a major Y Combinator success story: Parse cofounder and former chief executive Ilya Sukhar. Parse, which provides a mobile backend for developers to build apps on, was part of Y Combinator’s Summer 2011 batch, and Facebook acquired it less than 2 years later, in April 2013.

Sukhar was also the first employee at Etacts, a Winter 2010 batch company Salesforce later acquired, and has been investing in Y Combinator startups including Checkr, Apportable, Boostable, and Front.

Seibel’s Twitch.tv is of course another success story, selling to Amazon for just under $1 billion.

Y Combinator is currently between batches, having recently sent out acceptance letters for its upcoming session, which, as mentioned, is larger than any of its previous groups. But the accelerator also seems to be working on bringing experts in areas that more mature companies come to face, starting with former Twitter chief operating officer Ali Rowghani, who joined last month. At the time of the announcement, Y Combinator president Sam Altman explained that some of the accelerator’s most successful alumni companies are starting to face more advanced challenges, areas Rowghani and Sukhar can surely help with.

But that also raises the question of whether Y Combinator might be looking to accept more and more mature startups as well. It’s already accepted some with prior funding and traction, such as Algolia ($1.5 million in funding already) and Quora, which has been around since 2009 and has raised $161 million to date. Perhaps Y Combinator is quietly considering going beyond the baby startups it’s been nurturing so far.