Grigoryev left his wife Vasilyev and two children

Grigoriev left his wife Vasilyev and two children and refused to pay child support for their maintenance. He stated that he did not recognize the oldest child as his own, since three years ago he had learned that the child was not his, although he was recorded in the registry office in his name. In addition, the defendant said that he is currently married to Petrova and has two children whom he contains. Vasilyeva asked the court to invalidate Grigoryev’s marriage with Petrova, since her marriage with Grigoryev had not yet been dissolved, and thus release Grigoryev from the obligation to support children born in an invalid marriage. She demanded the recovery of alimony for the maintenance of her children without reducing their share.
Solve the problem.