She is the biological daughter of Nadia and Kaspian(leader of an Eastern European mutant tribe called the Beast-Men. In 1961, after Nadia's disappearance and Kaspian's arrest, Natalie and her twin brother Nick Furst were adopted and raised by Dr. Furst, thus forming the first nucleus of members to be known as the First Family.
By their pre-teens, Natalie and her brother, were joining their adopted grandfather and uncle on their adventures and discoveries, leading to the group becoming the First Family.
In 1979, she married Rex Zorus, the son of one of the First Family's major enemies, Madame Majestrix. While it was still shocking to some at the time, that she would choose to be with such a creature, the seeds of the romance had been planted in their teens.
In late 1972, Rex led an army from Monstro City against the surface world that were turned away by the First Family. But soon after Rex started to have a change of heart towards his mother's wishes to conquer the surface world and started to ally himself with the First Family.
Natalie held an attachment or crush on Rex almost from the start. She expressed a great fear at the possibility of him being taken away by the authorities for his role in the fall invasion, early the next year. The Fursts held steadfast that Rex changed his ways and protected him and even left Astro City for a period.
A few years later during the Family's tour of the Ring of Worlds it was evident that Natalie's feelings were becoming stronger, after becoming angry with Rex for flirting with an alien princess.
Expanding The Family
In May of 1986, Natalie gave birth to her and Rex's only child, Astra Furst. While there was likely some wonder how Astra would come out, she came out a beautiful healthy girl. Albeit one with spectacular energy powers and becoming the most famous grandchild on the planet.
By 1986, Astra grew bored of her "normal" life and longed for an adventure in the real world. She left without giving any specifics, which led to Natalie and the family searching all over heavens and the earth for her. Astra was discovered a few days later in one of the suburbs and Natalie gave her a good grounding. But she also realized the need Astra had to be around people her own age and to try and have a normal life. She let Astra continue going to public school among other activities.
Natalie channels a rare kind of energy internally through her body, whereas he brother's powers are manifested externally. She can build it up to increase her mass, growing in size, reaching even giant dimensions if she chooses. Alternately, she can tamp down the energy, decreasing her mass. While she does not decrease in size, she can lower her density this way so as to become intangible. Her energy sometimes discharges from her eyes, a the telltale sign of the forces coursing through her body.
This energy is also deployed by her brother, her daughter, and it seems to also be the same force that Augustus' energenerator wields, albeit in different ways.