Q1
What does "he had fathered a child out of wedlock."(4th paragraph) mean?
Does it mean he became a father by adopting a child??

Q2
What does "In stepped his sister Rose" (4th paragraph) mean?

Context
In the summer of 1910, Evangeline Simpson Whipple told the caretaker of her home not to move anything in her absence. The wealthy widow was going on a trip, but would be back soon, she said.

She never returned. When she died in 1930, she was buried at her request in Italy next to the love of her life — a woman with whom she had a relationship that spanned nearly 30 years. That woman, Rose Cleveland, had served as first lady.

The letters, preserved by the caretaker at Evangeline’s Minnesota home, are collected in a new book, “Precious and Adored: The Love Letters of Rose Cleveland and Evangeline Simpson Whipple,” and make clear that they were more than just friends, according to its editors.

When Grover Cleveland took office in 1885, he was a 50-year-old bachelor, a fact that almost derailed his campaign when rumors spread that he had fathered a child out of wedlock. (He had.) Protocol for unmarried or widowed presidents called for a female relative to fill the role of first lady. In stepped his sister Rose.

She was seen as an important counterbalance to her brother’s scandalous baggage: She was respectable, well-educated, a former teacher at a women’s seminary and the author of serious books.

Question

Q1
What does "he had fathered a child out of wedlock."(4th paragraph) mean?
Does it mean he became a father by adopting a child??

Q2
What does "In stepped his sister Rose" (4th paragraph) mean?

Context>>>>>>>>>>>>>>>>
In the summer of 1910, Evangeline Simpson Whipple told the caretaker of her home not to move anything in her absence. The wealthy widow was going on a trip, but would be back soon, she said.

She never returned. When she died in 1930, she was buried at her request in Italy next to the love of her life — a woman with whom she had a relationship that spanned nearly 30 years. That woman, Rose Cleveland, had served as first lady.

The letters, preserved by the caretaker at Evangeline’s Minnesota home, are collected in a new book, “Precious and Adored: The Love Letters of Rose Cleveland and Evangeline Simpson Whipple,” and make clear that they were more than just friends, according to its editors.

When Grover Cleveland took office in 1885, he was a 50-year-old bachelor, a fact that almost derailed his campaign when rumors spread that he had fathered a child out of wedlock. (He had.) Protocol for unmarried or widowed presidents called for a female relative to fill the role of first lady. In stepped his sister Rose.

She was seen as an important counterbalance to her brother’s scandalous baggage: She was respectable, well-educated, a former teacher at a women’s seminary and the author of serious books.

Muuluzi · Accepted Answer

There were rumors that emerged saying that Grover had had fathered a child out of wedlock. The rumors were true.
He did not marry the mother because apparently he was a bachelor. (so he couldn't have been married)

He did not marry his relative.
The protocol (the rule) was that if the president was widowed or had no wife, there had to be some sort of female as the first lady. So he allowed his sister to be the first lady (but did not marry her)

Muuluzi · Answer

1. ''To father a child'' is to be a father to a child. 
''out of wedlock'' a child born 'out of wedlock' means the child was born before the parents were married. 
So lets say A meets B and they have sex. Then B becomes pregnant so A either 1. marries the lady 2. takes care of the child or 3. leaves
2. His sister Rose stepped in to fill the role of first lady (see the previous sentence)

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