Hm… One idea could be to build a single contract which is a combination of TokenTimelocks timelocking-logic and on top of this the other logic of the TeamVesting-contract directly inside.
The logic of the TeamVesting contact is just that only 10% per month of all token can be released per beneficiary. Therefor I had encapsulated this logic inside a separate contract because I thought, I can put this contract then as beneficiary into TokenTimelock, which seems to not work.