My dad had bipolar, my sister and brother and I had therapy off and on for a few years, but then my dad finally got stuff under control, no longer had manic or deeply despressive episodes he once had.

I deal with my own depression right now, and do my best to keep my two kids from dealing with any of it.
My 10 year old I have talked to about depression, not about my own issues, but that feeling sad sometimes is normal, but if it's all the time, then we want her to talk to us, or her therapist or anyone she's comfortable with (she has had some times when she waS sad for quite a while, particularly when m mom and grandma died), so she knows some about it
My 7 year old, we talk about feelings frequently, but haven't really discussed depression. When he is older, we will because I want him to know that he can talk to us, or anyone he needs to if it happens to him.

Have my kids had to deal with my mentaal illness? Yes, indirectly when I was hospitalized, but they have never had to parent me or take care of me, because I make a concerted effort to assure that doesn't happen, because I admit my illness, and because I have help.

Unfortunately, a lot of kids have to deal with stuff they shouldn't have to, and I don't think that will ever change. I think all we can do as parents is to make sure kids get to be kids and get the help we need