Attending funeral of colleague's mother in law. Inappropriate?

Curious to get people's opinion on this. Working in a small company (5 employees). My colleague's mother in law passed away and my boss is nudging for himself and me to attend the funeral. My read is it's inappropriate to attend as the colleague wouldn't be the 'main' mourner if that makes sense - moreso his wife and her family.

What do you guys think? Am I overthinking?

UPDATE: Thanks everyone, very polarising opinions but very helpful! In the end, I was talking to my boss about it a few minutes ago, and my colleague (graceously) and politely declined our attendance - saying there was no need. We're going to instead put together a nice condolences message on RIP and a mass card.