Can I claim my 19 year old sibling as a dependent?

Our household consists of

myself (34) and i made 22,259. brother (18 in 2017) turned 18 on january 3 and was still a high school student till graduation on june 4, 2017. while he was in school he only worked on the weekend after graduation he works full time. he is not attending college just working. He made 15,1339 in 2017. He pays his cell phone bill and the internet. and sometimes helps pay a utility here and there. he is 19 since january of this year. I have claimed him as a dependent while he has been in high school. can i still claim him as a dependent for 2017?

my father gets ssi benefits that amount to a little over 13,000 and my mother worked a seasonal job in which she made 5469. my father's benefits are not taxable. since myself and the 27 year old brother bring in higher income than either of my parents, can my parents be claimed as dependents on our taxes? 

 There is also a 15 year old brother who is claimed by the 27 year old brother as a dependent. he made around 16,000. I also claim a 20year old sister who made 6033. she is a full time student and only works in the summer when she is off school. during the school year she lives in a dorm and comes home on the weekend but i provide her support.