Complex sentence: The genotype → environment model states that as siblings and fraternal twins age, their phenotypes grow apart due to their respective mastery of the passive, evocative and active interactions, which then play a role in differentiating their niches.
Split into simpler sentences: The genotype → environment model states that as siblings and fraternal twins age, their phenotypes grow apart. This is due to their respective mastery of the passive, evocative and active interactions, which then play a role in differentiating their niches.