But Deronda's first endeavor as he drove homeward was to convince himself that there was not the slightest warrantable presumption of this Ezra being Mirah's brother; and next, that even if, in spite of good reasoning, he turned out to be that brother, while on inquiry the mother was found to be dead, it was not his--Deronda's--duty to make known the discovery to Mirah. 
But as he drove home Deronda tried to convince himself that there was not the slightest likelihood of this Ezra being Mirah's brother; and that even if he did turn out to be, and if the mother was found to be dead, it was not Deronda's duty to make the discovery known to Mirah. 