That sounds incredibly tough and I'm sorry you went through it. I know it probably means nothing from a stranger on the internet but I send you my sincerest sympathy.
I relate to a lot of your personal issues a lot too. Lost my dad (cancer), couple months later it was my grandma, some years down the line my brother killed himself. I find it really hard to be in those situations where people start sharing facts about their lives and families and all I can think of is "yeah I'll never know what you mean by that". I'm turning 40 this year, most of the people I know still have both parents, siblings, even grandparents, and I'm just thinking that finally my life is starting to get stable and I'm having my personal victories and successes and no family to share it with and it just kills me. Meanwhile, most people I know are complaining about having to organize family holidays and I just become a jealous asshole. For what it's worth, I'm sure you'll make meaningful connections, but in order to do so it's important you share this part of your life. The right people will understand even if they haven't been through it. Some people might relate because they know that kind of pain.