Whether related or not, it depends on whether both parents are carriers. Relatives would have more chances of being silent carriers.
For any Autosomal Recessive disorder it's the same. It's called autosomal recessive inheritance. Autosomal means the gene is located on any chromosome except the X or Y chromosomes (sex chromosomes). Genes, like chromosomes, usually come in pairs. Recessive means that both copies of the responsible gene must have a disease-causing change (pathogenic variant or in the old parlance just a mutation) in order for a person to have the disease.
A person who has an autosomal recessive disease receives a gene with a pathogenic variant from each of their parents. Each parent is a carrier which means they have a pathogenic variant in only one copy of the gene. Carriers of an autosomal recessive disease usually do not have any symptoms of the disease. When two carriers of an autosomal recessive disease have children..... Then,
There's a 25% (1 in 4) chance that each child will not have the disease or carry the disease
There's a 50% (1 in 2) chance that child is a carrier but will not have the disease
There's a 25% (1 in 4) chance that each child will be born with the disease
