Hello
I also have two siblings, I have a younger sister who was 14 (now 25!) when my dad died and an older brother who was 18 (now 30!) When my dad died. I found it was the same actually, we never cried together as a family. My mum was very open about her grief and I often sat with her for hours while she cried and cried but I found my brother and sister couldn't deal with it and often left the room. I also rarely cried with her, choosing to let it all out when I was alone in bed at night or when noone was home. I honestly don't remember seeing my little sister cry, though I'm sure she did.. she seemed to sail through the grief somehow while my brother and I were the ones that struggled. My brother was actually with my dad when someone was trying to revive him, so he had different things to deal with than I did and I think because my sister was always closer to my mother (although of course she loved my dad just as much!) she still had someone to support her, whereas I was so close to my dad I literally felt like my world was crumbling. Of course, I loved my mum too, but I was so incredibly close to my dad. We often all talk about my dad, but I don't think we've ever actually discussed "grieving" together. You probably have already noticed how differently everyone grieves.. it is so hard to deal with someone elses grief when you're hurting yourself.
I tried to just be there with my mum she was upset, I'd just sit and cuddle her when she cried although it was very difficult. I remember there was a couple of times she was so upset we ran for the neighbours who eventually had to ring the doctor and my mum would scream at the doctor and ask him for something to put her to sleep so she didn't have to deal with the hurt anymore. Those were the hardest days of my life. Mum eventually realised she needed extra help and she sought the help of a psychiatrist and she would often tell me if it wasn't for my brother, sister and I she would have killed herself. It is not easy to see someone you love hurting so intensly, especially when you are too.
I think really what we all say we wish we had someone to talk to and that is the very best advice I can give you. Just be there with your mum when she wants to talk or just cry, try and encourage her to be open and likewise, be open with her if you want to cry or talk! You are very right though.. noone wants to burden someone else with their grief and I think that is why my mum eventually spoke to a psychiatrist because she didn't want us to watch her hurting anymore. Don't be surprised if your mum keeps to herself, especially with children that are so young, mum's are notorious for wanting to "keep it together" for their kids! Maybe you could just even tell your mum not to be scared to upset you, you want to be there for her. There might even be someone on here that's been through the loss of a partner that can tell you how they felt when they were grieving and were looking after their own children and what helped them cope. I think it must be hard having such a younger child in your family and teenagers because of course you will have more of an understanding about things than a 7 year old.
It is hard to hear sayings like "things happen for a reason" and that things will get better eventually.. and even having lost someone I still hate those sayings. I even had a friend at school ask me three weeks later at the start of school if I was over it yet!! All I can say is that you never "get over it" but you do learn to find ways to cope over time.
I have to say though, I miss my dad every single day so anniversaries and birthdays don't make me miss him anymore or less.. I always miss him, no matter what the date.