I was a missionary at a Japanese non-denominational Christian church in Osaka. In my experience—mostly limited to my own church, though I was able to visit several other churches, and attend a couple conferences with churches from all over the country—people didn't refer directly to each other as "brothers" or "sisters" (not like I do here in America with other men in my church), but sometimes about each other.
"Brother(s)"—[兄弟]{きょう・だい}
|
Direct |
Indirect |
| One person (<name>兄弟) |
× Never happens - Just follow normal name conventions (～さん, ～くん, name only, etc.) |
? Very rare - Just follow normal name conventions (～さん, ～くん, name only, etc.) |
| Group of men |
○ Mostly when preaching to - 「兄弟たちよ、祈りましょう！」; although probably not if you don't know them well
○ Addressing your own group in a familiar way |
○ Occasionally - あの兄弟(たち) "Those brothers" |
"Sister(s)"—[姉妹]{し・まい}
|
Direct |
Indirect |
| One person (<name>姉妹) |
× Never happens - Just follow normal name conventions (～ちゃん, name only, etc.) |
? Never heard it, but I could see a man referring respectfully to a younger woman this way, like 花子姉妹 |
| Group of women |
△ Men might address a very close group of women that way
× A group of women would probably never address themselves or another group this way |
△ Sometimes by men - あの姉妹(たち) "Those sisters"
× Never by women |
And then you can combine them as 兄弟姉妹 to refer to a mixed group, but this would be mostly indirectly.
As for the pastor, we would use <name>さん, <name>先生, or sometimes just 先生. These were all used both directly and indirectly. The term for pastor is [牧師]{ぼく・し}, but this would only ever be used in a high-level, or matter-of-fact statement (うちの教会の牧師は…). You would never use 牧師 in place of 先生 when addressing them, or referring to them by name.
Unfortunately, I have no experience with, or knowledge of Catholic terms in Japanese, so I cannot help you on that front.
