Father passed away but still legally married to his first wife?

My father recently passed away and he had a 1st wife and a 2nd wife (my mother). He got divorced in 2008 from his second wife but apparently he was never divorced from his first wife. Him and his first wife got married in Mexico in 1968 and about 5 years later he got married with my mother in Mexico. All the sibilings had agreed to split his assets 5 ways (i have 1 full brother and 3 half sibilings). But does she have a legal claim to his assests also? Thank you.