Objection 1. It would seem that spiritual relationship is not an impediment to marriage. For nothing is an impediment to marriage save what is contrary to a marriage good. Now spiritual relationship is not contrary to a marriage good. Therefore it is not an impediment to marriage.
Objection 2. Further, a perpetual impediment to marriage cannot stand together with marriage. But spiritual relationship sometimes stands together with marriage, as stated in the text (Sent. iv, D, 42), as when a man in a case of necessity baptizes his own child, for then he contracts a spiritual relationship with his wife, and yet the marriage is not dissolved. Therefore spiritual relationship is not an impediment to marriage.
Objection 3. Further, union of the spirit does not pass to the flesh. But marriage is a union of the flesh. Therefore since spiritual relationship is a union of the spirit, it cannot become an impediment to marriage.
Objection 4. Further, contraries have not the same effects. Now spiritual relationship is apparently contrary to disparity of worship, since spiritual relationship is a kinship resulting from the giving of a sacrament or the intention of so doing [See next Article, ad 3: whereas disparity of worship consists in the lack of a sacrament, as stated above (Question 50, Article 1). Since then disparity of worship is an impediment to matrimony, it would seem that spiritual relationship has not this effect.
On the contrary, The holier the bond, the more is it to be safeguarded. Now a spiritual bond is holier than a bodily tie: and since the tie of bodily kinship is an impediment to marriage, it follows that spiritual relationship should also be an impediment.
Further, in marriage the union of souls ranks higher than union of bodies, for it precedes it. Therefore with much more reason can a spiritual relationship hinder marriage than bodily relationship does.
I answer that, Just as by carnal procreation man receives natural being, so by the sacraments he receives the spiritual being of grace. Wherefore just as the tie that is contracted by carnal procreation is natural to man, inasmuch as he is a natural being, so the tie that is contracted from the reception of the sacraments is after a fashion natural to man, inasmuch as he is a member of the Church. Therefore as carnal relationship hinders marriage, even so does spiritual relationship by command of the Church. We must however draw a distinction in reference to spiritual relationship, since either it precedes or follows marriage. If it precedes, it hinders the contracting of marriage and voids the contract. If it follows, it does not dissolve the marriage bond: but we must draw a further distinction in reference to the marriage act. For either the spiritual relationship is contracted in a case of necessity, as when a father baptizes his child who is at the point of death--and then it is not an obstacle to the marriage act on either side--or it is contracted without any necessity and through ignorance, in which case if the person whose action has occasioned the relationship acted with due caution, it is the same with him as in the former case--or it is contracted purposely and without any necessity, and then the person whose action has occasioned the relationship, loses the right to ask for the debt; but is bound to pay if asked, because the fault of the one party should not be prejudicial to the other.
Reply to Objection 1. Although spiritual relationship does not hinder any of the chief marriage goods, it hinders one of the secondary goods, namely the extension of friendship, because spiritual relationship is by itself a sufficient reason for friendship: wherefore intimacy and friendship with other persons need to be sought by means of marriage.
Reply to Objection 2. Marriage is a lasting bond, wherefore no supervening impediment can sever it. Hence it happens sometimes that marriage and an impediment to marriage stand together, but not if the impediment precedes.
Reply to Objection 3. In marriage there is not only a bodily but also a spiritual union: and consequently kinship of spirit proves an impediment thereto, without spiritual kinship having to pass into a bodily relationship.
Reply to Objection 4. There is nothing unreasonable in two things that are contrary to one another being contrary to the same thing, as great and small are contrary to equal. Thus disparity of worship and spiritual relationship are opposed to marriage, because in one the distance is greater, and in the other less, than required by marriage. Hence there is an impediment to marriage in either case.
Source: Summa Theologica (New Advent)