Ulreich wrote on Instagram: "It is with deep sadness that we would like to announce today that our son Len passed away a few weeks ago after a long, serious illness.
"The decision to make this public now is incredibly difficult for us however, it is an important step for us as a family to create clarity in our environment and also in the public eye. Together with our daughter, we are now trying to find our way back to life step by step.
"A special thank you goes to our families, friends, and FC Bayern Munich for their discretion and great support over the past few months that means a lot to us.
"We ask the public and media representatives to be considerate and respect our privacy. We kindly ask you to refrain from further inquiries or statements. Lisa & Sven."