If the husband is the woman’s wali, can he get himself married to her?
Question

                I want to marry my cousin. She is my paternal cousin. I am her wali according to a shar’ee guardianship. I want to marry her but we do not have close relatives or brothers. There is no one else apart from me who can be her wali. Is it permissible that I say to her: “I give you myself in marriage” then she says: “I accept” in witnesses’ presence? Or shall I ask the marriage contractor to be her wali? What shall I do?.
Praise be to Allah.If a woman’s guardian 
    (wali) with regard to marriage is her cousin (son of her paternal uncle) and 
    he wants to marry her, there is nothing wrong with that if she agrees. 
Ibn Qudaamah (may Allaah 
    have mercy on him) said: 
The wali of a woman for 
    whom it is permissible to marry her may be her cousin, her master, the judge 
    or the ruler. If she gives him permission to marry her then he may do that. 
    End quote. 
Al-Mughni 
    (7/360). 
In that case he may do the 
    marriage contract on behalf of himself and the woman, because he is her 
    wali. So he says: I marry you, or I marry myself to So and so, and so on. He 
    does not need to say I accept, because his acceptance is implied. And she 
    does not need to say I accept either, because a woman cannot do the marriage 
    contract for herself or for anyone else, rather her wali does the marriage 
    contract for her. 
Or he may appoint another 
    man to do his marriage contract on his behalf, whether this wakeel is a 
    state official or someone else. In that case his deputy (wakeel) says: I 
    give you So and so in marriage, and he says: I accept. Thus the marriage 
    contract is done. Both ways are narrated from the Sahaabah (may Allaah be 
    pleased with them). 
Imam al-Bukhaari (may 
    Allaah have mercy on him) said: 
Chapter: If the wali is the 
    suitor. Al-Mugheerah ibn Shu’bah proposed marriage to a woman when he was 
    her next of kin (her guardian), so he told another man to do the marriage 
    contract for him. 
‘Abd al-Rahmaan ibn ‘Awf 
    said to Umm Hakeem bint Qaarit: Will you put me in charge of your affairs? 
    She said: Yes. He said: Then I offer to marry you. 
‘Ata’ said: Let him bring 
    witnesses, or let him order a man among her family. End quote. 
Al-Albaani classed the 
    reports of al-Mugheerah ibn Shu’bah and ‘Abd al-Rahmaan ibn ‘Awf (may Allaah 
    be pleased with them) as saheeh in Irwa’ al-Ghaleel, 1845 and 1855. 
It should be noted that it 
    is essential to have the marriage contract witnessed in both cases. For 
    information on the essential parts and conditions of marriage, please see 
    the answer to question no. 2127. 
End quote. 
And Allaah knows best.