Pattern hair loss — by far the most common kind — is strongly genetic, and the genes involved come from both sides of your family, not just your mother's father as the old myth says.
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Baldness comes from your mother's side. Half true and the half people skip matters. One important gene does sit on the x chromosome, which men get from their mother, but more than 200 other regions of the genome have been linked to hair loss, and those come from both parents. So look at your mother's father if you like, then look at your own father too.
Genetics load the gun, but the timeline is personal: two people with the same family history can start thinning decades apart and progress at very different speeds. That is why doctors care less about your family tree than about what your scalp is doing right now and how fast it is changing.
Whatever your genes say, the useful move is a doctor's assessment now rather than later — and with Uberhair that first assessment happens from home, from guided photos you take on your phone.