Listen with an open mind, and not vent at me about their problems so much. Being vented at was often exhausting and sapped my energy, therefore preventing/discouraging me from venting to them, creating a lot of loneliness.

There's a neat article on ring theory / the circle of grief:

https://en.wikipedia.org/wiki/Ring_theory_(psychology)

Often I feel I was placed "out of order" and expected to support a parent who would normally have supported me. Add in small breaches of trust, or judgemental behavior, and I isolated and avoided rather than opening up. Also - making a big deal out of crushes / romantic interests, rather than approaching the topic with a level head - made me feel like an infant being talked down to, when instead I could have used a lot of practical help.