There are multiple definitions - click on the translation that matches your context.

entidad depositaria

full

custodian

noun

Comparative law notes

Spain

for investment and pension funds–fondos de inversión y de pensiones

Definitions of custodian

English

a person who has responsibility for looking after property or something else of value or importance, or who has custody of someone (= the legal right or duty to care for a thing or a person)

You need to name a custodian and list the property you're leaving to your child.