1 and 2 — For the first couple of years, Zephyr became an alcoholic. He felt broken and regretful of his actions, and beer and other substances seemed to be the only cope. This took a big toll on Zip’s early life. Zephyr tried not to neglect his child, but from always being intoxicated, Dumbbell mostly cared for Zip. He was their biggest influence in their life, and always would be there for them no matter what. Slowly, and painfully, Zephyr became fully sober, and planned to stay that way. Things were looking better for the family, and things were going better.
3 — Zip loves their aunt. While Zephyr was an alcoholic, she was also their for them. (This was before Sona was born, so Flutters had a lot more free time)
4 — As the years went on, and Zip got older, their mental health started to deteriorate. Due to their father (the one who literally birthed them) not being there made Zip started to think he didn’t want to be there. But did he? Though they had lots of support through these hard times, Zephyr never really knew what to do about it.
I not many mental illness characters pop up in mlp (or if they do, it’s stupid). But, Zip suffers from depression, and it plays a role in their arc.