Bio oil is actually harmful. Try not to use that. I use cocoa butter
Bio oil and cocoa butter lotion ;)
Try really hard to not gain too much weight too fast. Don't worry about "showing" it will happen. And yes genetics are a factor, stay moisturized.
It's genetic. You can't prevent them. You can make them lighter with lotions, but can't prevent them. You either get them or you dont.
Vitamin e helps, some lotions or oils have it. Its not always preventable, some women get it even with creams.