What happens if a heir won’t respond to ad litem?

My dad didn’t leave a will and hadn’t spoke to his son in 12 years. He is in CA and early June I went to court to become temporary administrator over estate because my attorney couldn’t contact him and when she did he was rude. Ad litem came into place June 15th and I was told last week ad litem hasn’t been able to get him to respond and we need him to sign papers so I can become permanent administrator. He can’t be admin. due to being out of state and a lengthy criminal record. My attorney said if he doesn’t respond that he’s still entitled to half of everything even if he won’t comply. She told me earlier in the year that he only has so long that he can not comply before he basically loses out. Now I’m confused and can’t figure out what to do next. I’ve had to beg 6 weeks for my attorney to contact me and she finally did she hasn’t been much help.