Board Thread:Naruto Gaiden/@comment-32622248-20170719100834/@comment-31405103-20170726204640

When a Jinjuuriki has a child, that child is born with the whiskers. Hence Naruto having them because his mother was Kurama's Jinjuuriki at the time of his conception, and his children having them since he is Kurama's Jinjuuriki now. So, yes, it is because of Kurama.