@Grace84,
1. liking FB anything means nothing. I have one friend who likes every single thing they see - to acknowledge they've seen it. that is all it means. it means nothing about interest. Nothing.
2. if you wanted to get to know him - you should have asked him out.
3. what do you mean ignore him? it's not like you're seeing him to begin with.
4. friendly terms? you're not seeing him - there is no friendship - he is a real life acquaintance. that's it.
5. you aren't dating. how are you planning to fall for him. you are not in a relationship with someone because they like your FB posts/statuses
6. you want to know how long he's known his relationship person? you have to ask him
7. if you're interested in someone - ASK THEM OUT. yes, I am yelling. ASK PEOPLE OUT IF YOU ARE INTERESTED.