Hair color changing

Fr

My son was born with a head full of black hair and around 2 months old it started falling out & around 4 months old he was completely bald ! He’s now 6 months and his hair is growing back nicely but now it’s really light !! Like a ashy brown and in the sun it’s golden.

no one in my family has this hair color and nobody on dads side has this hair color either so we are puzzled on how he got it 😂. Has this happened to anyone?