Finding that the father has contributed ~1/4 of his genes to the child would normally exclude them from being described as the biological parent, who would norm

Finding that the father has contributed ~1/4 of his genes to the child would normally exclude them from being described as the biological parent, who would normally contribute ~1/2 his genes to the child. Possibly the father had no brothers, therefore no-one else could contribute even 1/4 of the genes (unless the child is a chimera from two fathers...).