For many years, people thought that a cross between Schlumbergera microsphaerica and other members of the Schlumbergera family was impossible.
However, Ralph Mangelsdorff did succeed in crossing S. microsphaerica with S. truncata. Ruud Tropper started to make crosses with S. kautskyi, S. opuntioides and S. x buckleyi and was successful in raising seedlings of these hybrids. As doubt did exist, Michal Barfuss of the University of Vienna conducted DNA analysis and was able to confirm the parentage of the new crosses, where one of the parents was indeed S. microsphaerica. The full article on this topic can be found in the EPIG Journal 83 (2020).
An English abstract of the article can be found here: