If it's fifty-fifty between genders, and each birth is an independent event, but a boy + girl is like umm.. a chain of independent events or something? My gues

If it's fifty-fifty between genders, and each birth is an independent event, but a boy + girl is like umm.. a chain of independent events or something? My guess is 25% - 0,5 times 0,5.. But what exactly is the right answer? There doesn't seem to be a consensus yet.