In 1861 it says he is b. Paris.
Rather speculative, but you might want to look into a possible connection with Eugene Boileau (~1813-1869), of London, engraver/artist, b. France, may have naturalised in 1862. He lived in Clerkenwell from at least 1854 (patent notice) to 1861 (census).
There was also a Pierre Etienne Boileau, m. 1833 in St. Pancras to Candelaria Frilet. In the 1861 census he is listed as aged 79, b. Geneva, to his wife's 54 (b. Cadiz, Spain). Daughters are Mary and Amelia. In 1841 he is aged 55. He probably died in 1863 (indexed as Peter Stephen Boileau).
Now, familysearch.org shows a Pierre Etienne Boilleau had a son Pierre Louis Eugene Boilleau ("Pierre Louis" could be baptismal names, this boy could have gone by Eugene day to day), with (wife) Marie Charlotte Vetter baptised in Paris in 1814. This could easily be the same man who married in London in 1833, perhaps taking his son(s?) from his first marriage with him.