baby hair loss, when does it usually happen?

What stage do they go through the bald patch so to speak?
for my sister it was six months, and I never lost all of my hair because I had so much of it but I was seven months. My youngest sister was nearly one when her hair fell out then it regrew
our LO has tons of dark hair but its starting to get strands of blonde, and I have seen bald babies around the age of 3-4months or some are born with little to no hair but just curious

DS Liam was born with a huge thick mat of dark hair - it started to fall out 3-4wks after he was born and gradually over 2mths or so he went fully blonde....
DD Rhiannon was born with fine dark hair that very very slowly started shedding from the week after birth and was replaced with fine blonde hair by the time she was 4.5mths old. She has very fine hair so at nearly 2 it's finally thickening up a lil bit lol smile
hers was so slow and gradual she never looked balder than at birth or anything! Liam's was patchy for a month of the colour change in his hair lol. Very patchy!

DD started losing hers around 6 weeks i think, although she never fully lost all her hair. And i have noticed in the last week or two that it is getting thicker again, still doesn't have much hair but its growing back slowly. I started noticing the hair loss when there were all little hairs all over her bed wink