Jenelle Evans and her ex-fiancé Nathan Griffith reached an agreement over custody of their 6-year-old son, TMZ reports.The Teen Mom 2 alum, 28, will retain primary physical custody of Kaiser, according to court documents obtained by the website on Tuesday, October 20. Griffith, 33, will have custody of their son every other weekend, and his mother, Doris Davidson, will care for her grandson every fifth weekend.