When I was at BA you had to complete 12 months’ service before parental leave was an option. Then, you could email them and they’d email back with dates available for your fleet / seat. They were accommodating in so far as they have to offer it but not so accommodating with regards to when it was available. Ultimately family life was unmanageable for me as a junior longhaul FO who lived more than 2 hrs from LHR.