Hi
I cant find deaths for deaths for them either

But I have found something else quite interesting... Francis Burdett Coutenay was a naughty boy again, he did have another child in 1851. FRANCES MARIA COURTENAY, possible birth registration March Qtr. 1851 as Frances Maria Burdett.
She is on the census with him in 1871 when he's widowed but not before, and is an executor in his probate record.
And her marriage details
3rd April 1878 All Souls Church
Walter Miller Lambert bach full age Captain RMA of Miltn, Portsea. Father: Richard Lambert~ gentleman of Lyston Hall, Essex
Frances Maria Courtenay a spins. full age of Langham Place St Marylebone. Father: Francis Burdett Courtenay ~ surgeon
Both signed register.
Trying to find out who her mother is

I'm intrigued !!
claire