I'll give y'all the Catholic Encyclopedia (New Advent) Article on Mary Tudor:
Queen of England from 1553 to 1558; born 18 February, 1516; died 17 November, 1558. Mary was the daughter and only surviving child of Henry VIII and Catherine of Aragon. Cardinal Wolsey was her godfather, and amongst her most intimate friends in early life were Cardinal Pole and his mother, the Countess of Salisbury, put to death in 1539 and now beatified. We know from the report of contemporaries that Mary in her youth did not lack charm. She was by nature modest, affectionate, and kindly. Like all Tudor princesses she had been well educated, speaking Latin, French, and Spanish with facility, and she was in particular an accomplished musician. Down to the time of the divorce negotiations, Mary was recognized as heir to the throne, and many schemes had been proposed to supply her with a suitable husband. She was indeed affianced for some time to the Emperor Charles V, the father of the man she was afterwards to marry. When, however, Henry VIII became inflexibly determined to put away his first wife, Mary, who was deeply attached to her mother, also fell into disfavour, and shortly afterwards, in 1531, to their great mutual grief, the mother and daughter were forcibly separated. During Anne Boleyn's lifetime as queen, the harshest treatment was shown to "the Lady Mary, the King's natural daughter", and wide-spread rumours affirmed that it was intended to bring both the princess and her mother to the gallows. However, after Queen Catherine's death in January, 1536, and Anne Boleyn's execution, which followed in a few months, the new queen, Jane Seymour, seems to have shown willingness to befriend the king's eldest daughter. Meanwhile very strong pressure was brought to bear by the all-powerful Cromwell, and Mary was at last induced to sign a formal "submission", in which she begged pardon of the king whom she had "obstinately and disobediently offended", renounced "the Bishop of Rome's pretended authority", and acknowledged the marriage between her father and mother to have been contrary to the law of God. It should be noted, however, that Mary signed this paper without reading it, and by the advice of Chapuys, the imperial ambassador, made a private protestation that she had signed it under compulsion. The degree of favour to which Mary was restored was at first but small, and even this was jeopardized by the sympathy shown for her in the Pilgrimage of Grace, but after the king's marriage to his sixth wife, Catherine Parr, Mary's position improved, and she was named in Henry's will, next to the little Edward, in the succession to the throne.
When Henry died it was inevitable that under the influences which surrounded the young king, Mary should retire into comparative obscurity. She chiefly resided at her manors of Hunsdon, Kenninghall, or Newhall, but during Somerset's protectorate she was not ill-treated. When the celebration of Mass was prohibited, she summoned up courage to take a strong line. She wrote to the Council and appealed to the emperor, and it seemed at one time as if Charles V would actually declare war. Throughout, Mary remained firm, and despite repeated monitions from the Council and a visit from Bishop Ridley, she to all intents and purposes set the government at defiance, so far, at least, as regarded the religious observances followed in her own household. At the same time her relations with her brother remained outwardly friendly, and she paid him visits of state from time to time.
At Edwards's death on 6 July, 1553, the news was for some days kept from Mary, Northumberland, the Lord President of the Council, having contrived that the young king should disinherit both his sisters in favour of Northumberland's own daughter-in-law, Lady Jane Grey. The Lord President, backed at first by the Council, made a resolute attempt to secure the succession for Lady Jane, but Mary acted promptly and courageously, setting up her standard at Framlingham, where the men of the eastern counties rallied round her and where she was soon joined by some members of the Council. By 19 July Mary had been proclaimed in London, and a few days later Northumberland was arrested.