I had my first at 20 so was a younger mum. I made loads of mum friends, most of whom were about 10-15 years older than me. I met people at baby groups that I'm still friends with now, 19 years later. I hope they didn't have any negative feelings towards me, they certainly didn't show it off they did. They helped me with some things, like offering me second hand furniture when I moved into my first flat with DD, moving out from my parents house, or looking after DD on odd occasions when I needed to be at uni and my childcare fell through. I helped them with other things, like babysitting sometimes (DD was portable and I didn't have a partner to worry about), or taking their dc1 to activities when their dc2 was a small baby (I used to take a friend's DD to toddler swimming with me every week for about 6 months). We were friends, so that's what friends do, age doesn't come into it.
My second DD came along when I was 30, so no longer a younger mum, but not an older mum either. My friends with children the same age as dd2 ranged in age from 21-48 at the time of giving birth. I've stayed friends with the older mums from that group, but that's not because I thought anything about the age of them, I just had more in common with those particular women. And my life is busier now, so I have fewer close friends.
The only things I sometimes think about really young mums (teen-agers) is "I wonder how she's coping". Because i know I wouldn't have coped at 16/17/18. I barely coped at 20, and that was living with my parents who gave a massive amount of support. And I am glad dd1 has not gone down that road of being a very young mum, as it does mean you miss out on things.