I dont find it so much of an age thing all the time. I would class someone as a young mum if they were under 25 (usually when your under 25 is when you get the dirty looks). I went to TAFE with a 37 yr old and i was 18 and we were great friends, she had a daughter the same age as mine so it worked out great, she was single/seperated and didnt act so much like a 37 yr old, honestly when she told me her age i was shocked, i thought she was more like 27. hehe
It's all about finding someone who has things is common with you and not necessarily the same age although i admit she is my only friend who isnt under 25.