Can you marry a lady you helped to abort pregnancy belonging to another man who deny ownership of the baby?
Yes, you can marry a lady you helped to abort pregnancy belonging to another man who denied ownership of the baby BUT on one condition - that you BOTH REPENT and confess the sin to Christ because abortion is a sin and should be regarded as such.
After a genuine heart-felt confession and repentance, then believing that Christ Jesus has forgiven you, you must never support such act again or in any way condone it. Then, you can now go ahead to marry and put the past behind you because that's where it belongs.
The power to save and forgive belongs to God and there's no sinner He will cast out once you confess and repent of those sins. He said in Ezekiel that He does not want the death of a sinner but that the sinner should repent and come unto Him. Jesus also said in the gospel of St. John that He will never cast out WHOEVER comes to Him.
Remain richly blessed..