If mark celebrated his 8th birthday 10 years ago then mark is 18 years old. Jess is twice as old as mark so Jess is 36 years old. Julie is 26 less than mark and jess combined so Julie is 28 years old. Gwen is two years older than Julie so Gwen is 30 years old. The twins are 2 less than 1/3 of gwen so the twins are 8 years old