I can't spend time with my mum?

I'm 18 years old and I live with my mum and 2 year old brother. I rarely get to spend time with my mum by myself as my brother is a lot to handle, so it's difficult to ask family if they can look after him for an hour so I can spend time with my mum. I can't spend time with my mum in the nights either as he's not in a bed time routine, I keep asking and asking my mum to get him into a routine so I can spend an hour with her alone before she goes to bed but she usually just mocks me when I ask. She allows my brother to sleep whenever he wants throughout the day and then let's him go to bed at around 10pm but by the time he's asleep; she's too tired to stay awake and just spend an hour with me. I rarely spend time with her as her focus is always on my brother and keeping him occupied (which I understand) but I guess it just makes me sad that there's never enough time for her to spend with me.