10.5 Month Old Won't Sit unsupported...should I Worry?

I wouldn't worry about this at all and I'll tell you why.
My daughter started walking at 7 months.....NO, I'm not exaggerating. To this day, it's just about the weirdest thing I've ever seen, but I know another mama on here and I have talked privately, her baby was walking at 7 months too. Anyway....my mother in law used to joke that my daughter would be in kindergarten and have to be tied to her chair to keep her from rolling off. My daughter wouldn't sit for more than a few seconds unattended. She rolled over every time and then it was drag herself to something to stand up on so she could take off walking.
Your baby crawls and cruises so I think it's the same thing as with my daughter....why waste time sitting around? :)
She sat in her high chair and didn't wobble over and that's why I wasn't worried. She could hold herself up, she basically just didn't really feel the need to much. She was always on the move.
Since your baby can squat down and not sit, sounds like he's got some strong little legs and good balance.
He just has what Grandma called "round bottom syndrome".
He'll get the hang of it.
I really wouldn't worry.

Best wishes!

I would worry if he couldn't crawl, cruise, etc, but since he can do that - don't worry.

My oldest child refused (refused!) to roll over. I mean, just absolutely wouldn't do it. I was in a panic at the time because she hadn't reached this milestone. The pediatrician saw that she could pull up to standing, she was cruising, crawling, etc and told me not to worry - she was choosing not to roll over, but clearly her muscle tone was strong and she was coordinated. For the record, she's 8 now and a cheerleader and ballet dancer - her lack of rolling over as a baby was no indicator of her future agility!

Odd for sure. I think since he seems to be doing everything else just fine and you know he can do it, I guess I wouldn't worry about it, although I think I might too! ;) Seriously though, he's probably just fine.

Do you have Parents as Teachers in your area...check it out and sign up for it ASAP! It's a super awesome FREE service provided through your school district. I asked my PAT lady a ton of stuff like this b/c she was much more convenient and she came to me! They do home visits and provide you with so much amazing info! It rocks, seriously!! Do it!!

Overall, he sounds like an active little guy! He's just too busy to sit apparently!

have you tried feeding him when he is on the floor? or give him a bowl of cheerios while he is sitting?

He may have something called "Low Tone" or Hypotnia in his muscles.Check with your Ped about it or have him checked by a Developmental Pediatrician. He needs to work on those muscles and you may need to try Physical Therapy with him. How are his other milestones? If there are any significant delays, Hypotonia is a possible factor. Other than that, maybe he's just a motivated little bugger and wants to keep moving !!! Good Luck! xx