Question on ownership

hi , I have a slightly complicated question.

My father in law purchased and apartment many years ago in fueringola with his ex wife. They paid cash for the apartment and when he and his wife split he kept the apartment as part of the agreement.

He never received the deeds in his name (due to the lawyer at the time )and had been trying to get this sorted recently with another lawyer

. He was told that if he remained the owner of the property for 30 years and continued to pay all the bills then he would be able to get the deeds in his name. The 30 years has now expired in march however he sadly passed away last april , leaving 2 daughters (one my partner) . We have the keys for the apartment and the bills are up to date as he left money in the Spanish account to pay.

What is the law regarding this ? any help would be appreciated.

Thanks

Simon