I am aware the question is extremely broad (beyond what can be said generally - like what the Church's view was, which would count as 'paneuropean', excluding other religions and the fact that local and social laws often trumped religious interdictions), and I don't expect any answer to be comprehensive, only to include an example from a specific time and place, especially of an evolution (e.g. a totally made up one, but maybe in 13th century Italy half-siblings both inherited from the father, but in the 14th century this evolved to a system where elder ones got priority, something like that).