Maria's second husband was Prince Ferdinand of Saxe-Coburg-Kohary (1816-1885), son of Prince Ferdinand of Saxe-Coburg (who was uncle to both QV and Albert) and his wife the very rich Hungarian Princess Antonia Kohary. Maria married Ferdinand in 1836, after having been widowed at age 16 the previous year. Queen Victoria and Albert from this point on maintained close relations with the Portuguese Royal Family. Unlike his cousin Albert, who was only made a Prince Consort, Ferdinand was made titular King of Portugal, reigning with his wife as Ferdinand II. After Maria II died in childbirth in 1853, Ferdinand was later married to an Elizabeth Hensler (in 1869).
As for Maria's children:
Peter V and Stephanie: I've heard of no pregnancies of this couple, Peter I know died of typhoid, I'm not sure of Stephanie. Both died so young, Peter in 1861 and Stephanie in 1859.
Louis, succeeded his brother and married Maria Pia of Italy (dau. of Victor E. II), they had two sons: Charles, who along with his eldest son Louis Philip were assassinated in 1908; and Alfonso, who married a Nevada Hayes (an American, I think).
John, Duke of Beja 1842-1861, I believe he also died of typhoid.
Mary Anne married King George of Saxony and had a large family.
Antonia married Leopold of Hohenzollern-Sigmaringen. Among her descendants are King Ferdinand of Roumania and his brood. She had another son, William, who was the father of Augusta Victoria of Hohenzollern who married the last and exiled king of Portugal, Emanuel II. They remained childless and Emanuel died fairly young in England.
Ferdinand 1846-1861. He would have only been 15 at his death. I'm not sure, but I believe I've read that there was a typhoid epedemic in Portugal, and this son may have also been a victim. I remember reading that these deaths were one of the blows that contributed to the death of Prince Albert in 1861.
Augustus, Duke of Coimbra 1847-1889. I have no information on this son.
Hardly a stable dynasty.