Just trying to understand this neighbor?

There's this over 15 years older than me neighbor in front of whom i blushed hard 10 years ago and he teased me about liking him. He never made any contact with me or my mother until recently (a year or two, when I turned 20) when he started greeting her with 'Good Afternoon' and last time the informal 'hello' and my mom is over 60 and never had anything with those neighbors, not even chit chat.

we bumped into each other some days ago and he was staring at my face passing by, then couple days later he is in his yard (so that i can see him) and is gardening and planting with his baby next to him (for which he had no need other than brag).

So i'm not planning on having anything with a married man and not intending to start talking to him or be a home wrecker but I am curious why does he do that?
Just trying to understand this neighbor?
Post Opinion