All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.
We hope that you have taken the initiative to repent after marriage. For more benefit, please refer to Fatwa 86527.
There is a difference of opinion among the jurists about the ruling on the marriage of an adulterer (or fornicator) with the woman whom he committed Zina with before they repent; some of them permitted it and some have forbidden it. The issue is a matter of Ijtihaad.
Since your marriage has been concluded and according to the Ijtihaad of some jurists it is permissible, then it is considered to be valid, especially with the length of time and after having children.
The children that you have from this marriage are traced back to you, so you do not have to renew the contract.
For more benefit on the marriage of a fornicator (adulterer) with the woman he committed Zina with before repentance, please refer to Fataawa 329617, 188393, 158403, 135767, 95615, and 86903.
Allah knows best.