You appear to be stating that you found subtenants for your apartment, the landlord approved the sublease, and that your landlord was originally going to enter into a new lease with your subtenants in December but, due to their failure to pay their rent on time, is no longer willing to do so. The subtenants appear content to remain in the apartment.

You have not told us when your present lease term ends, or if your lease would renew or continue month-to-month based upon the presence of the subtenants at the end of its term. If the lease will soon end and will not renew or continue, then it may be that the best solution is to allow the subtenants to remain in occupancy until your lease expires -- at which time their presence becomes your landlord's problem. If the lease will not soon expire and you're worried that they're not going to pay rent, or if their presence will cause your lease to automatically renew or continue on a month-to-month basis, then it makes sense that you're concerned about getting them out (or convincing your landlord to change his mind about entering into a new lease with them).

I have no access to your lease agreement with your subtenants, so I have no way of determining if you leased to them for a fixed term (e.g., all remaining months of the lease) or if you leased to them on a month-to-month basis. If the former, their being late a couple of times on the rent, with your never having issued them a notice to quit for nonpayment, is not going to rise to the level of a material breach of the lease -- that is, it won't support an action to evict them. If they're month-to-month tenants, you can serve them with a thirty-day notice and, if they don't move within the notice period, you can file an action in court to evict them.