certification of relationship or proof of kinship

hi im kathy from philippines, im an english teacher here in jilin province and i just get back last june 18 2017 with my 3 kids and my brother as my companion. My kids has an s1 visa and my brother has s2 Chinese gov said we can pro long or extend my brothers visa if we have a certification of relationship or proof of kinship. all of our birth cert has been authenticated by our local gov and chinese embassy. im just wondering how to get certification of kinship for my brother in the philippines and if is it possible if were here in china? thanks.