The short answer for this is that all the ahadith quoting Maryam or other women (he was not married with) among Muhammad's () wives in Paradise are either weak or rejected, there's no single sahih narration in that issue.
According to this (only in Arbic available) fatwa on islamqa #111279 their are narrations quoting that Muhammad () will marry in paradise Maryam daughter of 'Imran (the mother of 'Isa), Assiyah daughter of Muzaahemthe wife of Pharao and Koulthoum the sister of Musa ().
In the tafsir of Verse (66:5)
Perhaps his Lord, if he divorced you [all], would substitute for him wives better than you - submitting [to Allah ], believing, devoutly obedient, repentant, worshiping, and traveling - [ones] previously married and virgins.
Ibn Kathir seems to have quoted a hadith of at-Tabarni in his al-Mu'jam al-Kabir on the authority of Buraidah saying the interpretation that Allah has promised our Prophet to marry him, the previously married woman refers to Assiya the wife of Pharao and the virgins to Maryam daughter of 'imran. But the narrator chain of this hadith is weak as the person Salih ibn Hayyan صالح بن حيان who heard Buraidah is weak and rather unreliable if there's no backup for his narration.
It was also narrated on the authority of abu Hurraiah in at-Tabarni's al-Awsat in a long hadith quoting the Prophet's () relation with -his slave- Mariya al-Quibtiyah in the house of his wife Hafsa in which he quoted that among his previously married wives (in Paradise) there will be Assiya daughter of Muzahim the wife of Pharao and the sister of Nuh () and among the virgin Maryam daughter of 'imran and the sister of Musa(). At-Tabarni already added that this hadith was narrated on abu Hurriarahs authority only by Hisham ibn Ibrahim هشام بن إبراهيم and his narrations are regarded as munkar (rejected), as he is considered as an unknown by many great scholars such as a-Dhahabi and ibn Hajjar al-'Asqalani!
The fatwa also quotes 5 more ahadith on that topic which were not quoted in any tafsir, but all of them are quoted in less reliable hadith compilations such as the books of at-Tabarani (whom in first place tried to create a hadith encyclopedia by collecting all available hadith narrations he was able to hear at his time), ibn 'Assakirs Tarikh Dimashq, al-'Oqayli's "a-Do'afa' al-Kaber" (a book on known weak narrators), and other compilations which are not of the first choice if one seeks at least hassan hadith.
