Why does he keep mentioning his children?

So this guy is not someone I'm dating, he's a colleague at work and I've been having the feeling that he's kind of into me. He seems to be stalking my online profiles because he keeps mentioning stuff that's only on there, he looks at me softly but also seriously, comes very close, makes all kinds of excuses to have more time together, blushes, ... all those kinds of things.
And he also often mentions his children. But not his wife/girlfriend. If it were for the info I have from him, I could think that he doesn't have a partner, but it seems that he does, ultimately.

Now, it's just making me wonder a lot. If he's actually flirting with me and coming on to me, what does the mentioning of his children mean? Does it mean 'don't get your hopes up, I already have a family' or what? Fine, then I won't, but why does he keep literally coming on to me? Or am I imagining this? If he wants to stay away from me, he could just also mentions his wife/girlfriend.
I actually like him as a person but I don't know what to do with his behaviour, it throws me off a bit. We could just be friends but his semi-flirting is honestly interfering with that.
Why does he keep mentioning his children?
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