Not sure what to do?

I am 22 and live/look after my 4 younger siblings, I have been since our mother passed in 2008, the youngest is 15 (girl),16(girl),17(boy),20(girl) the 16 n 17 yo both have partners n are never home or want to spend anytime at home when they are home they don't really talk they just do there own thing in the house, the 15 yo does not have a partner n spends a lot of time at home but in her room I try to talk to her but she keeps conversation small n doesn't talk very much, I as well do spend time in my room but do try to make an effort to have family meetings to see how everyone is and discuss how I'm feeling, but it doesn't change the 16 n 17yo still go off with there partners n the 15yo keeps to herself and the 20yo we don't really get along, her partner lives with us too and she always with him 24/7 we all talk occasionally but we don't really do anything, I don't feel like this is normal but I don't know what to do?