public IEnumerable <Person> GetBrothersInLaw() { var bil = new List <Person>(); var spouseMaleSiblings = Spouse?.First().Relationships.GetSiblings() ?.Where(x => x.Gender == Gender.Male); if (spouseMaleSiblings?.Any() == true) { bil.AddRange(spouseMaleSiblings); } var femaleSiblings = Siblings?.Where(x => x.Gender == Gender.Female) ?? Enumerable.Empty <Person>(); foreach (var motherFemaleChild in femaleSiblings) { var spouse = motherFemaleChild.Relationships.GetSpouse(); if (spouse?.Any() == true) { bil.Add(spouse.First()); } } return(bil); }