Yes Devi Ganga was married and possibly more than once according to this story of domestic strife that happened in the Vaikunth. Devi Puran Book 9 Chapter 6 mentions that Lakshmi, Ganga, Saraswati were all the wives of Lord Vishnu and lived with the Lord till a quarrel happened between the last two:
16-21. Nârâyana said :-- Hear, O Nârada! I will now describe that incident, the hearing of which removes all the sins. Laksmî, Sarasvatî and Gangâ, the three wives of Hari and all equally loved, remain always close to Hari. One day Gangâ cast side-long glances frequently towards Nârâyana and was eagerly looking at Him, with smile on Her lips. Seeing this, the Lord Nârâyana, startled and looked at Gangâ and smiled also. Laksmî saw that, but she did not take any offence. But Sarasvatî became very angry. Padmâ (Laksmî) who was of Sattva Guna, began to console in various ways the wrathful Sarasvatî; but she could not be appeased by any means. Rather Her face became red out of anger; she began to tremble out of her feelings (passion); Her lips quivered; and She began to speak to Her husband.
Lord Vishnu perhaps realizing that he should best remain out of a the women's argument left the place and then started the curses and counter curses. Saraswati tries to attack Ganga but Lakshmi intervenes so gets cursed by the former. Seeing this Ganga gets angry and curses Saraswati:
39-44. Thus saying, Gangâ became ready to curse Sarasvatî and addressing Laksmî, said :-- “O Dear Padme! As that woman has cursed you to become a river, so I too curse her, that she, too, be turned into a river and she would go to the abode of men, the sinners, to the world and take their heaps of sins.” Hearing this curse of Gangâ, Sarasvatî gave her curse, “You, too, will have to descend into the Bhurloka (the world) as a river, taking all the sins of the sinners.”
When all the action is over Lord Vishnu returns and tells them:
45-67. O Laksmî! Let you be born in parts, without being born in any womb, in the world as the daughter in the house of the King Dharma-dhvaja. You will have to take the form of a tree there, out of this evil turn of fate. There S'ankhachûda, the Indra of the Asuras, born of my parts will marry you. After that you will come back here and be my wife as now. There is no doubt in this. You will be named Tulasî, the purifier of the three worlds, in Bhârata. O Beautiful One! Now go there quickly and be a river in your parts under the name Padmâvatî.
O Gange! You will also have to take incarnation in Bhârata as a river, purifying all the worlds, to destroy the sins of the inhabitants of Bhârata. Bhagiratha will take you there after much entreating and worshipping you; and you will be famous by the name Bhagirathî, the most sanctifying river in the world. There, the Ocean born of my parts, and the King S'ântanu also born of my parts will be your husbands.
O Bharatî! Let you go also and incarnate in part in Bhârata under the curse of Gangâ. O Good-natured One! Now go in full Amsas to Brahmâ and become His wife. Let Gangâ go also in Her fullness to S'iva. Let Padmâ remain with Me. Padmâ is of a peaceful nature, void of anger, devoted to Me and of a Sâttvika nature.
So going by this account Ganga was first married to Lord Vishnu, then Lord Shiva, and then Shantanu.
Bhishma Pitamah was her son from Shantanu.