"As a female foreigner whose relationship with Jason was only formalized with the birth of the children, Medea would have been viewed as an irregular companion, and after Jason's betrothal to Glauce, she would be reduced to the status of concubine." (Guastella in Claus) This makes them a helpful tool in securing her bond to Jason. Another means by which they can be useful props for Medea is when she sends them carrying poison to their new step-mother. Medea spends time with them to make and carry out plans to kill her enemies, but she does not spend time with them out of love. "Jason and Medea's two children function as her primary props, her greatest source of power." (Taggle)

Although the relationship is a focal point of Euripides' play, it is not a play about the relationship between mothers and children. The children are not complete characters in the play, but moreso props that are used by other characters. The children are...

Additionally, they are tools which she can use to obtain things she wants, such as the death of the children's step-mother. In the end, Medea is able to kill the children without a second thought because her relationship with them is built purely on her own needs, not on loving them as her own kin.
Works Cited

Euripides. Medea. Trans. Ian Johnson. http://www.mala.bc.ca/~johnstoi/euripides/medea.htm

Guastella, Gianni. "Il destino dei figli di Giasone (Euripide, Ovidio, Seneca)." In Clauss, James. University of Washington. 2000. http://omega.cohums.ohio-state.edu/mailing_lists/BMCR-L/2002/0162.php

Tagle, Steven. "The Dramatic Appeal of Human Props in Greek Drama." Stanford University. 9 March 2004. http://www.stanford.edu/~stagle/ESSAYS/WIN%20IHUM33A%20E02%20HumanProp.htm