Modern Australians are much more sensible about relationships. Many openly acknowledge that the relationship aught only last as long as both are getting something from it. Meanwhile they understand the need to be parents to their children regardless of their own relationships.
The problems with changing relationships are actually a product of religious "death do us part no matter how bad it gets" model. They load the whole idea of moving on with as much guilt as possible.
Church attitudes, including the stigma on unmarried parents is the foundation of unhealthy attitudes in relationships. Moreover the church has always placed the man in control and expected women to play the minor role in marriage.
More enlightened attitudes have moved the norm beyond the primitive, ignorant notions that form the foundations of religious doctrine.
Handled compassionately and with dignity, a separation need not be eternally traumatic for anyone involved. The experience of the children comes from the attitude of their parents to each other.
My wife's ex and his partner are among the very best of our friends. All our children consider themselves as one big family. When asked in class our eight year old granddaughter listed her eight "grandparents".