For context, I'm a gay man.
First off, I'd say you can't know for sure. But if there's strong evidence in his social media to make you think that he is gay, it seems a reasonable thing to at least consider.
If he is gay and I'll repeat that it's a big if here I wouldn't ask him. It doesn't matter how 'OK with it' you are; for a young person, the realisation and self-acceptance around stuff like this is extremely delicate... and personal. It almost doesn't matter if he knows that everyone in his life would react well; there's still a considerable (and extremely difficult) personal journey to go on internally.
So it's for him to tell you, not for you to ask. Coming out is, ultimately, about truth. It's a correcting of the record about who a person is, but the empowerment is in the person themselves making the statement. Asking him would, in my opinion, risk making him feel like you'd taken agency away from him in some way.
Just make sure the relationship you have and the environment at home is conducive to him feeling safe and loved, regardless of his sexuality. If he knows that the family home is a safe place for him if he is gay, even if he doesn't come out for a few more years, it'll help.
To everyone casting doubt at knowing at a young age... agreed, two seems very young. But I definitely had an awareness of it when I was seven or so. Obviously it wasn't sexual in any way. But I used to have happy little daydreams about one day marrying one of the fashion models from the menswear section of my mum's Kays catalogue! When grannies etc used to make remarks about me marrying a 'nice girl one day' I used to run off and cry because the idea of it felt so wrong, so uncomfortable to me.